Hi guys
I have a problem which is haunting me . I get the same fault i my beers, and i feel like ive tried everything to get rid of it. Its an bittering astringency on the back of my tongue when i taste the beer. I think its aceto bacteria, but how do i get rid of it? I made a starter 3 days ago with extract and safale yeast(as a test). What am i doing wrong?
1: I clean all glassware(including stopper and airlock) and pot with soap.
2: Leave all the items(not the pot) in no rinse Iodophor for 30 min while boiling the extract.
3: pouring the boiled beer into the glass and add stopper and airlock while cooling.
4: added the yeast, replaced stopper and airlock, placed in dark 68 degree room, and waited 3 days.
5: tasted the starter and STILL got the same fault.
I need some help here in Denmark

I've never come across a bacterial contamination that i would describe as bitter. Acetobacter I associate with tartness, as it produces acetic acid, which is essentially vinager.

I would stop using soap, first. Get a percarbonate-based cleaner, like B-Brite. Here we can buy a cheap household cleaner/laundry additive called Oxyclean that is the same chemical, perhaps you have the same thing or something like it, it's a non-chlorine bleach. This cleans brewing equipment very well without the problems associated with soap, having little flavor, rinsing well, and having less impact on head retention.

An added benefit of this type of cleaner is that a 10-30 minute exposure will do a decent sanitizing job. Combined with the final Iodophore sanitization, you will be well protected against infections. If you want to make sure you start clean, a dilute bleach solution, say 1-5%, will kill just about everything it comes in contact with in 10 minutes.

I fear that you may be experiencing the dreaded "extract twang" that can come from old extract or extract that is boiled too long at a high concentration. If you are boiling half your total final volume, only add 1/3 to 1/2 the extract at the beginning of your boil. Add the remaining extract about 15 minutes before the end of your boilo and see if that improves things.

Another option would have been astringency from your steeping grain, but that wouldn't have appeared in your starter. Another consideration would be your water. If your water is high in certain minerals, like sulfates, your beer can tend to be harsh.

One last point. Be sure to allow your beers to age a bit. Many beers will be a little harsh at first. By around 8 weeks, most normal alcohol beers will have smooted out considerably.

I tried some new things while making a starter. i used a cleaner based on percarbonate called chemipro oxi, a non-chlorine bleach. and i decided to try some water testing while i was at it, and used demineralised water.

and wouldnt you know the weird aftertaste disappeared

I dont think it was my cleaning that caused the fault, but my water, i didnt consider it before your post, but we have very hard water. im not sure about the sulfate level or other minerals.

Will boiling the water before brewing help this water problem? i know this will remove most of the hardness, but will it remove sulfate or other water content?

You can try diluting your water with either distilled or deionized water to reduce the salt concentrations. You can get reverse osmosis systems to treat your own water if it is too costly to buy treated water.

You should probably try to get a water analysis from your town to see what your water has in it, instead of continuing blind. They are generally available in the U.S., so maybe there as well. There are also companies or university labs that will do water testing for a minimal cost, usually $10-30 in the U.S..